Alkali metal composition additives for fuels of the gasoline range



United States Patct 3,532,147 Patented Feb. 20, 1962 This invention is directed to novel alkali metal compositions as soluble fuel additives for use in spark-ignition engines, and more particularly to such compositions having significantly and unexpectedly improved inductibiiity characteristics.

The novel compositions of this invention are comprised essentially of an alkali metal compound and an amino-amide as more fully described hereinafter. They are significantly valuable in improving the combustion characteristics of liquid hydrocarbon fuels for spark-ignition engines, e.g. the resistance of such fuels to knock is improved.

The alkali metal compounds with which this invention is concerned are derived from branched chain carboxylic acids. Though very efiective to improve the combustion characteristics of fuels for spark-ignition engines, they are rather involatile compared to the normal fuel components and, as a result, are not always cleanly and completely inducted into the combustion chamber in those systems where satisfactory inductibility of the fuel charge depends at least in part on the volatility characteristics of its components. For example when a carbureted engine is operated on gasoline containing an alkali metal carboxylate, deposits of metal salt, owing to its involatility, appear throughout the induction system and eventually their build up in the carburetor jets and in the intake manifold is such as tocause malfunctioning of the engine.

In engines equipped with fuel injection systems the problem presented by the formation of deposits in the induction system is less severe. It may be avoided entirely of course by injecting the fuel charge (or the alkali metal component) directly into this combustion chamber. However, where the fuel charge is injected into the intake manifold, deposits may again form, around the intake ports of the combustion chamber for example, to ultimately impede the passage of fuel into the chamber.

Another problem related to the inductibility of fuel additives is that of insuring equal distribution of the additive to all cylinders of the engine. This is particularly important when the additive is an antiknock, since any one (or more) cylinders which did not receive its share of additive could knock even though the other cylinders were operating knock-free.

It is an object of the present invention to provide novel alkali metal additive compositions for use in spark-ignition engines. It is a further object of this invention to provide novel alkali metal additive compositions that are soluble in and inductiole with liquid hydrocarbon fuels for spark-ignition engines. It is still a further object of this invention to provide carburetable compositions containing an alkali metal carboxylate as described, which carboxylate heretofore was normally not carburetable with liquid hydrocarbon fuels. These and other objects will become apparent in the following description and claims.

More specifically, the present invention is directed to a fuel-soluble and fuel-inductible additive composition for use in liquid hydrocarbon fuels for spark-ignition engines, which composition is comprised essentially of (1) an alkali metal carboxylate compound consisting of an alkali metal salt of a branched chain carboxylic acid and from 0 to 10 moles per mole of said salt of a branched chain carboxylic acid, in which salt and acid a C to C hydrocarbyl radical is attached to the carbon atom of the carboxyl group through a non-aromatic carbon atom and (2) from an equal to a 10-fold amount by weight based on the alkali metal salt of an aminoamide of the formula,

N H1) n Where R singly is H or a lower alkyl radical, R singly is an aliphatic hydrocarbyl radical; R and R together may be an alkylene or aikyleneether radical, R is a straight chain hydrocarbon radical; and, the carbon atoms in R, R and R total at least 11; where n is an integer from 2 to 3.

When used as an additive, the present novel composition will be present in a liquid hydrocarbon fuel for spark-ignition engines in an amount to provide at least 0.0025 gram of the alkali metal per liter of fuel.

This invention is based on the surprising discovery that an alkali metal carboxylate as defined, which normally is not carburetable with liquid hydrocarbon fuels, is readily inducted into the engine when in the presence of an amino-amide as defined,

The fuel-soluble and fuel-inductible compositions of the alkali metal carboxylate compound and the aminoarnide induction assistant may be prepared simply by mixing the individual components in the presence or absence of a solvent, in the proportions defined above. Also, the components, individually or in any combination, may be added directly to the fuel, and blended into it by stirring, to produce the final fuel composition. Al ternately a concentrate of the components may be added to the fuel in the desired amounts. The proportions of each component may vary from one composition to another but each will be chosen within the broad limits to provide optimum solubility and inductibility.

The amino-amides of the subject compositions are highboiling and thermally stable liquids that are miscible with gasoline and that have a pronounced solubilizing affect on the alkali metal carboxylates in such fuel. They may be prepared, as already described in the art, by reacting a straight chain fatty acid (or anhydride or acid chloride) with the appropriate diamine.

As indicated in the above formula the diamine reactant may be a monoor di-substituted aminoethylamine or similarly substituted aminopropylamine. In these, the substituents other than hydrogen may be monovalent hydrocarbyl radicals, or they may be divalent alkylene or alkyleneether radicals which together with the nitrogen constitute a heterocyclic ring. Examples of such diamines are 2-diethylaminoethylamine, 3-dimethylaminopropylamine, 3 piperidinopro-pylamine, 3 morpholinopropylamine, and 3-tallowaminopropylarnine where the tallow group represents a mixture consisting mainly of linoleyl, oleyl and stearyl radicals.

The straight chain carboxylic reactant may be either saturated or unsaturated, and have up to about 18 carbon atoms e.g. acetic, butanoic, decanoic, dodecanoic, tetradecanoic, oleic and stearic acids, and preferably will contain at least 10 carbon atoms so that R" will have 9 or more carbons. R and R of the diamine and R" of the carboxylic acid portions of the molecule will be chosen so as to total 'at least 11 carbon atoms, and preferably to total 13 to 22 carbon atoms, to provide gasolinesoluble amino-amides having the desired physical characteristics.

Representative aminoamides are:

These aminoamides are gasoline-soluble and have sufficiently low volatility and high thermal stability so that the evaporation loss does not exceed about 6 weight percent when they are heated for 8 hours at 275 F. using the test equipment described in ASTM D972-56. Their viscosities at 210 F. lie between 2 and centistokes.

The preferred amino-amides are those derived from the 3-diloweralkyl (C to C anu'nopropylamines, particu larly their oleamides.

The alkalimetal carboxylates with which this inven-' tionis concerned are the Li, Na and K salts of branched chain carboxylic acids which may be primary, secondary or tertiary acids, open chain or cyclic, in which the carbon atoms joined at the carbon atom of the carboxyl group is a non-aromatic carbon atom of a hydrocarbyl radical. More particularly the branched acids are those containing 5 to carbon atoms and having at least one branch in the carbon skeleton within the first 4 carbon atoms of the molecule, counting the carboxyl carbon atom.

Representative acids from which the alkali metal salts may be derived are: pivalic(2,2 -dimethylpropanoic), 2 ethylbutanoic, 3,3 dimethylbutanoic, 4 methylpentanoic, 4,5-dimethylhexanoic, 2-ethyl-2-methylbutanoic, 2-ethylhexanoic, 3,5,5-trimethylhexanoic, Z-heptylnonanoic, 2-hexyldecanoic, 2-ethyl-2-butyldecanoic, 2,2-di methyloctadecanoic, campholic(l,2,2,3-tetramethylcyclopentane-l-carboxylic acid), isofencholic, 3-methyl-3-cyclohexylbutanoic, 3-methyl-3-phenylbutanoic, 3-ethylpent- 3-enoic, 2,2-diethylbutanoic, and 1,4-diisopropylcyclohexane-l-carboxylic acid.

The branched acids may also be those obtained as complex mixtures either from natural sources or from synthetic processes. Thus, the acids may be the naphthenic acids from petroleum, or they may be mixed acids obtained by oxidizing branched chain aldehydes and primary alcohols produced by reaction of olefins (particularly branched chain olefins) with carbon monoxide and hydrogen in the well-known oxo-process. Examples of such readily available oxo-alcohols are the mixed octanols, decanols and tridecanols obtained from heptenes, nonenes, and dodecenes.

Also, the branched acids may be those obtained directly by carboxylating olefins (particularly branched olefins) with carbon monoxide and water in the presence of acid catalysts (e.g. boron fluoride, sulfuric acid) as described in the art. Examples of such acids are those obtained from such olefins as Z-methyIpentene-l, dodecene-l,

. mixed dodecenes, mixed tetradecenes, and'mixed octadecenes, including the dimers, trimers, tetramers, and

the comparable low molecular weight iuterpolymers, of

propylene and isobutylene. These mixed acids are generally complex in terms of branched carbon skeletons and the number of carbon atoms in the molecule. They maycontain as low as 5' (as in pivalic acid fromisobutylene) and as high as about 25 such as the C acid fraction produced along with the C acid fraction from the branched dodecenes. V V Mixtures of any of the above acids may be used for the preparation of the alkalimetal carboxylate component. a As stated, the alkali metal compound maybe the salt amides themselves have been found to be effective solubilizing agents for those salts whose, solubility in liquid hydrocarbon is limited, the carboxylic acids are even more effective for this purpose, and in the preferred embodiment of the invention at least about 1 mole and usually not more than about 3 moles of such acid per mole of salt will be employed. 7 The carboxylic acid is efiective to prevent the deposition of the alkali metal carboxylate from solution in the fuel, not only in storage (in the fuel tank), but in the induction system as well, where it assists the amino-amide in effecting passage of the'alkali metal compound through the carburetor and intake manifold and into the combustion chamber. The acids are particularly useful in combination with the lower members of the carboxylate series, e.g. the pivalate, and with amino-amides that are somewhat less eflicient solubilizers for the carboxylates, e.g. N-(3-morpholino propyl) oleamide.

The acid-salt compositions may be prepared simply by mixing an alkali metal carboxylate and a carboxylic acid of the defined class, in the presence or absence of a solvent. Alternately the acid-saltmixture may be obtained by partially neutralizing the acid to the desired extent with a suitable alkali metal base. These compositions may be prepared in a liquid hydrocarbon carrier such as benzene, toluene, heptane, isooctane, diisobutylene, kerosene, gasoline and blends thereof, which solvents are also useful for the preparation of concentrates.

The above alkali metal carboxylate compounds may be combined with the amino-amides in the presence or absence of solvents such as those listed above. The quantity of amino-amide will range from about one to ten times the weight of the alkali metal carboxylate, with the optimum quantities depending on, the particular alkali metal compound employed. In general, the higher ratios will be employed with the lower molecular weight alkali metal 1 compounds in general and with the Li compounds in paritself or the salt plus up to 10 molar proportions of a a .carboxylic acid of the above type. While the aminoticular. For example, whereas about an equal weight of N(B-dimethylaminopropyl)oleamide suflices to provide good results with Li naphthenate, about 4 times the Li 'pivalate weight will ordinarily be required for optimum performance in carbureted systems. Best results are generally obtained with at least a two-fold quantity of the amino-amides and ordinarily not more than a 5-fold quantity will be needed.

The compositions of this invention are adapted to provide working concentrations of the alkali metal in soluble and inductible form in media consisting essentially of liquid hydrocarbons. The hydrocarbon may constitute the major component or a relatively minor component of the solution, such as when they are dissolved in the fuel itself or when made up as concentrates for addition to fuels. For the preparation of concentrates, the liquid hydrocarbon media may be parafiinic, isoparaffinic, olefinic, naphthenic, aromatic or blends thereof. The compositions may also be incorporated as concentrates in other gasoline additives such as tetraethyllead anti-knock compounds. The fuels with which the alkali metal compositions are to be used are the liquid hydrocarbon fuels which comprise the various gasolines of commerce. .Such fuel may be a clear stock i.e. not containing additives, or it may be a finished commercial fuel containing additives normally associated with such fuels, e.g. anti-oxidants, corrosion inhibitors, anti-icing agents, anti-knocks, and scavenging agents for combustion products of such antiknocks. The term leaded fuel used herein means a fuel containing an antiknock quantity of tetraethyllead, e.g. 0.12 to 1.5 ml. per liter, and the appropriate scaven- 1girs, e.g. ethylene dibromide, ethylene dichloride and the l e. 1 The alkali metal compositions are eflectiverto improve the combustion characteristics of the fuel, and in particular the knock resistance of the fuel, and when so employed will be present, in quantities providing from about 0.0025 to about 2 grams, preferably 0.05 to 1.5 grams of alkali metal per liter. The quantity of amino-amide of these compositions will range from about 1 to 5, and preferably at least 2 times the weight of the alkali metal carboxylate. In the preferred embodiment, up to moles, more usually about 1 to 3 moles per mole of salt, of a branched chain carboxylic acid will also be present.

The compositions of this invention are adapted for use in carbureted as well as fuel injection systems. The complete explanation for the surprising inductibility of these compositions is not known. It is believed, however, that the amino-amides, with assistance from the carboxylic acids when present, maintain the alkali metal carboxylate in such a physical state that it can pass through the induction system with the rest of the fuel charge. In a carbureted engine the fuel is fed to the carburetor venturi section where it is partially vaporized in the air stream to produce a fuel-air mixture containing both vaporized and liquid fuel. The fuel-air mixture travels through the intake manifold, past the high temperature region in the intake port area (where at least a part of the liquid mist portion of the stream may also be vaporized), and into the combustion chamber. It is believed that the alkali metal compositions of this invention pass through the induction system principally as fine droplets of liquid, perhaps as part of the heavy ends of the gasoline, entrained in the fuel vapor-air stream; also, that this liquid portion of the fuel-air mixture may flow along the walls of the induction system and finally through the intake port, under the assisting pressure of the fuel-air stream.

It is considered unexpected that a carbureted engine can be operated on such a fuel containing a normally non-carburetable additive and remain substantially clean and free of objectionable deposits in the induction system. In marked contrast, when such an engine is operated on a fuel containing the alkali metal carboxylate, or the carboxylate-carboxylic acid composition, but not containing the amino-amide, a considerable portion of alkali metal compound is left in the induction system as solid or tacky deposits. Soon afterwards, the engine idles with difliculty and in time the passage of gasoline through the carburetor, etc, even at normal and higher engine speeds, becomes impeded entirely. S'nnilarly, in manifold fuel injection systems, where the build up of solid or tacky deposits around the intake ports of the cylinders eventually becomes intolerable. In addition to overcoming these difficulties, the amino amides of this invention provide for a rather remarkably uniform distribution of the alkali metal in the combustion chambers of multi-cylinder engines, with the result that over-all engine operation is smoother.

The marked effectiveness of the amino-amides as particularly defined cannot be attributed solely to their solubilizing action on the carboxylates or to whatever surfactant properties they may have, for a wide variety of substances that are effective either to solubilize the alkali metal carboxylates or to maintain the induction system clean when used in ordinary gasolines are practically ineffective to solve the present problem.

In the representative examples which follow, the inductibility test is one involving the use of a carbureted Briggs and Stratton single-cylinder gasoline engine, and, was developed for rapid screening and comparing of candidate induction assistants for normally non-carburetable substances. The results, with regard to carburetor fouling, intake manifold deposits and intake valve sticking, agreed with those obtained in the more conventional carbureted single-cylinder engines such as the CFR engines used in the motor method and research method for evaluating a fuels resistance to knock, and correlated with performance in full-scale multi-cylinder engines.

The test consisted of operating the engine at 2000 rpm. under light load conditions for hours running time, interrupted by 3 shutdowns of at least 4 hours duration to let the engine cool. Alternately allowing the engine to run and to cool, it was found, more nearly represented conditions pertaining in the every day use'of automotive engines, and the results obtained under these conditions were a better measure of the actual automotive performance of additives and of the effects of deposits on this performance than uninterrupted operation.

The base fuels employed were commercial gasolines, and the lubricant, whose nature did not affect the results, was either a multi-graded commercial oil or a lubricating oil base stock.

Under the test conditions described above none of the compositions of the present invention caused either fouling of the carburetor or malfunctioning of the intake valve, and to further rate these compositions, with regard to induction system deposits, the following merit scale was adopted.

DEPOSITS Siugle-Cylinder Ports and Intake Tacky Oily Weight grams Merit Rating Valve I 2 to 4 Heavy throughout 2 or over. 5 to 6 Light to moderate 1.5 to 2. 7 Trace Light N 0.5 to 1.5.

Light T 0.5. None d Below 0 5 do None... 0.

Compositions having merit ratings of less than 8 in this test are considered to be impractical for use in carbureted multi-cylinder engines.

Example 1 A lithium campholate-N(3-dimethylaminopropyl)-oleamide composition was prepared by stirring 1 part by weight of the salt with 2 parts by weight of the aminoa'mide at about C. until the mixture was homogeneous. When the mixture had cooled to room temperature, about an equal volume of leaded gasoline (0.8 ml. tetraethyllead/liter) was stirred into it and then the whole diluted with more of the leaded gasoline in quantity to provide a final composition containing 1.67 g. of the salt and 3.34 g. of the amino-amide per liter of gasoline.

Tested for inductibility according to the method described above, this fuel composition had a merit rating of 10.

Example 2 The method described in Example 1 was used to prepare the fuel'compositions designated as A to F below.

'Each contained, per liter of gasoline, 1.32 g. of lithium campholate, 2.64 g. of one of the amino-amides tabulated below, and, where noted below, 1.32. g. of a carboxylic acid.

FUEL-INDUCTIBLE Li CAMPHOLA'IE COMPOSITIONS Additives Composition Amino-Amide Carboxylie Acid Ii(3-dietbylaminopropyl)-o1eamide None. N (s-tallowaminopropyl)acetamide. Do. N(3-dimethylaminopropyl)-oleamid Pivalic. b1(Ii-morpholiuopropyD-oleamide... o. N(3-dimethylaminopropyl)-oleamide. Campholic. N (S-dimethylaminopropyD-strearamide Do.

Fuel compositions A through D had merit ratings of 9, and compositions E and F ratings of 8, in the inductibility test.

In comparative compositions, in which an equal weight of an amino-amide of a branched chain carboxylic acid, such as N(3-diethylaminopropyl) 3,5,5-trimethylhexanoamide or N(3-dimethylaminopropyl) ox'o-tridecanm amide, replaced the amino-amides of compositions A and B, valve sticking was observed in the inductibility test (merit ratings less than 2). The oxo-tridecanoic acid referred to above was prepared by oxidizing a commercial sample of the oxo-tridecanol obtained from tripropylene, carbon monoxide and hydrogen.

V 7 Example 3 a By the procedure of Example 1 there was prepared a blended gasoline composition containing 1.25 g. of lithium pivalate, 1.25 g. of pivalic acid, and 4 g. of N(3-morpholinopropyl)oleamide per liter. This composition rated 9 in the inductibility test.

Example 4 N(3-dimethylaminopropyl)oleamide raised the merit rating to 10.

Example 5 The procedure of Example 1 was usedto' prepare the inductible gasoline compositions containing the sodium and potassium carboxylates listed below. The'carburetion assistant, referred to as DMAPO in the table, was N(3- dimethylaminopropyl)oleamide. The fuel was a leaded automotive gasoline containing 0.8 ml. of tetraethyllead per liter. Merit ratings of these compositions in the inductibility test are also given below.

INDUCTIBLE GASOLINE-ALKALI METAL Li campholate and N(3-dimethylaminopropyl)oleamide were mixed and blended into a leaded gasoline by the procedure of Example 1. The blended gasoline thus prepared contained.1.3 g. of the Li salt'and 2.6 g. of the amino-amide, in addition to 0.8 mi. of tetraethyllead, per

liter of fuel.

The inductibility of the above blend in a multicylinder engine was determined in a Buick automobile engine 8 cylinders, compression ratio 11:1) under medium duty cyclic conditions.

The cycle involved running at an engine speed of 700 r.p.m. at 0 load for 1 minute, followed by accelerating to 2000 rpm. in 9 seconds at a load of 25 brake horsepower (B.H.P.) and holding under these conditions for 3 minutes and 19 seconds, followed by decelerating to 700 rpm. in 32 seconds at a load of 25 B.H.P. Coolant temperature was 155 F., oil temperature 150 F., .and airinlet temperature ambient.

The test duration was 150 hours during which about 1800 liters of fuel was consumed. Engine operation was normal throughout the run. Upon completion of the test, the engine was dismantled. The carburetor and intake manifold were found to be clean, andf'the stems and tulips of the intake valves normal. 7 a

"If the amino-amide is omitted from the fuel composition and instead 2 vol. percent of isopropyl alcohol is used (as a solubilizer for the Li campholate) the operation of the engine becomesv erratic within a few hours and soon it is impossible to idle the engine due to an accumulation of the Li salt in the carburetor jets.

Example 7 8 200 F.; jacket temperature, 212 F. When the engine was operated at spark advances of 19.5 and 26 BTC, the knocklimited performance of the above fuel. composition was 103.4 and 104.4 performance numbers, respectively. Under the same test conditions, the same fuel without the ,Li campholate/N-(3-dirnethylarninopropyl)oleamide additive rated 80.6 and 82.6 performance numbers, respectively. Thus, the additive mixture provided antiknock improvements'of 22.8 and 21.8 performance numbers. In contrast when the above aminoamide was replaced in the above fuel composition by two volume percent (based on the fuel) of isopropyl alcohol as a solubilizer for the Li campholate, and the fuel composition was rated under the same conditions at spark advances of 19.5 and 26 BTC, the performance numbers were 91.5 and 96.8, respectively, corresponding to increases of only 10.9 and 14.2, respectively;

Example 8 A composition consisting of equal weights of Li campholate, pivalic acid and N(3-dimethylaminopropyl)oleamide was evaluated for antiknock properties by the standard research method (ASTM D908-51). The fuel was a commercial premium gasoline having a performance number of 88.1 by the research method. Incorporating the above composition into this fuel, in an amount providing 1.67 grams of each of the 'campholate, pivalic acid and the amino acid, raised the performance number to 94.1.

The blended compositions of Examples 1-8 are smoothly inducted into carburetted CFR engines and show significant improvements in octane ratings versus the appropriate controls under the standard conditions of the motor and research methods of determining the octane ratings of fuels.

As many apparently widely diiferent embodiments of this invention may be made without departing from the spirit and scope thereof, it is to be understood that this invention is not limited to the specific embodiments thereof except as defined in the appended claims.

The embodiments of the invention in which an exclusive property or privilege is claimed are defined as follows: 7

1. A fuel additive composition soluble in a liquid bydrocarbon fuel of the gasoline boiling range, said additive composition being inductible with said fuel in sparkignition engines, said additive composition consisting essentally of (1) an alkali metal carboxylate compound consisting of an alkali metal salt of a branched chain carboxylic acid and from 0 to 10 moles per mole of said salt of a branched chain carboxylic acid, a C to C hydrocarbyl radical being attached to the carbon atom of the carboxyl group of said salt and said acid through a non-aromatic carbon atom, and, (2) from an equal to a 10-fold amount, by weight, based on said alkali metal salt, of an amino-amide having the formula /N(CH2)nN RI 7 fifRII or V wherein R singly is taken from the group consisting of hydrogen and a lower alkyl radical, R singly is an aliphatic hydrocarbyl radical, R and R together being taken from the group consisting of an alkylene and an alkyleneether radical, R" being a straight chain hydrocarbon radical, and, the carbon atoms in R, R and R" totalling at least 11, where n is an integer from 2 to 3, said alkali metal salt being present in anramount to provide from about 0.0025 gram to 2.0 grams of said alkali metal per liter of said fuel.

2. A fuel additive composition soluble in a liquid bydrocarbon fuel of the gasoline boiling range, said additive composition being inductible with said fuel in spark- 9. ignition engines, said, additive composition consisting essentially of (1) an alkali metal carboxylate compound consisting of an alkali metal salt of a branched chain carboxylic acid and from to moles per mole of said salt of a branched chain carboxylic acid, a C to C hydrocarbyl radical being attached to the carbon atom of the carboxyl group of said salt and said acid through a non-aromatic carbon atom, (2) from an equal to a 10- fold amount, by weight, based .on said alkali metal salt,

of an amino-amide having the formula.

monnnN R o-n" 3 wherein R singly is taken from the group consisting of hydrogen and a lower alkyl radical, R singly is an aliphatic hydrocarbyl radical, R and R together being taken from the group consisting of an alkylene and an alkyleneether radical, R being a straight chain hydrocarbon radical, and, the carbon atoms in R, R and R" totalling at least 11, where n is an integer from 2 to 3, and, (3) a liquid hydrocarbon solvent for (l) and (2), said alkali metal salt being present in an amount to provide from about 0.0025 gram to 2.0 grams of said alkali metal per liter of said fuel.

3. A liquid hydrocarbon fuel of the gasoline boiling range for spark-ignition engines, containing an additive composition consisting essentially of 1) an alkali metal carboxylate compound consisting of an alkali metal salt of a branched chain carboxylic acid and from 0 to 10 moles per mole of said salt of a branched chain carboxylic acid, a C to C hydrocarbyl radical being attached to the carbon atom of the carboxyl group of said salt and said acid through a non-aromatic carbon atom, and, (2) from an equal to a 10-fold amount, by weight, based on said alkali metal salt, of an amino-amide having the formula wherein R singly is taken from the group consisting of hydrogen and a lower alkyl radical, R singly is an aliphatic hydrocarbyl radical, R and R together being taken from the group consisting of an alkylene and an alkyleneether radical, R" being a straight chain hydrocarbon radical, and, the carbon atoms in R, R and R" totalling at least 11, where n is an integer from 2 to 3, said additive composition being present in an amount to provide from about 0.0025 gram to 2.0 grams of alkali metal per liter of fuel.

4. The liquid hydrocarbon fuel of the gasoline boiling range according to claim 3 wherein the additive composition is present in an amount to provide from about 0.05 guralm to about 1.5 grams of alkali metal per liter of said 5. The liquid hydrocarbon fuel of the gasoline boiling range according to claim 3 wherein from about 1 to about 3 moles of said branched chain carboxylic acid is present per mole of said branched chain carboxylic acid salt.

6. The liquid hydrocarbon fuel of the gasoline boiling range according to claim 3 containing from 0.12 to 1.5 ml. of tetraethyllead per liter of said fuel.

7. A liquid hydrocarbon fuel of the gasoline boiling range for spark-ignition engines containing an additive composition consisting of (1) an alkali metal carboxylate compound consisting of an alkali metal salt of a branched chain carboxylic acid and from 0 to 10 moles per mole of said salt of a branched chain carboxylic acid, a C to C hydrocarbyl radical being attached to the carbon atom of the carboxyl group of said salt and said acid through a non-aromatic carbon atom, and, (2) from an equal to a Ill-foldv amount, by weight, based on. the alkali metal salt, of an amino-amide. having the-formula I wherein R singly is taken from the.:group-consisting of hydrogen and a lower alkyl radical, R singly is an aliphatic hydrocarbyl radical, R and, R together being taken from the group consistingof an alkyleneand an alkyleneether radical, R" being a straight chain hydrocarbon radical, and, the carbon atoms in R, R and R" totalling at least 11, Where n is an integer from 2 to 3, said additive composition being present in an amount to provide from about 0.0025 gram to 2.0 grams of alkali metal per liter of fuel, said hydrocarbon fuel being a finished commercial fuel containing such additives as are normally associated with said fuels.

8. The liquid hydrocarbon fuel of the gasoline boiling range according to claim 7 wherein the additive composition is present in an amount to provide from about 0.05 gram to about 1.5 grams of alkali metal per liter of said fuel.

9. The liquid hydrocarbon fuel of the gasoline boiling range according to claim 7 wherein from about 1 to about 3 moles of said branched chain carboxylic acid is present per mole of said branched chain carboxylic acid salt.

10. The liquid hydrocarbon fuel of the gasoline boiling range according to claim 7 containing from 0.12 to 1.5 ml. of tetraethyllead per liter of said fuel.

11. A fuel additive composition soluble in a liquid hydrocarbon fuel of the gasoline boiling range, said additive composition being inductible with said fuel in spark ignition engines, said additive composition consisting of (1) An alkal metal carboxylate compound consisting of an alkali metal salt of a branched chain carboxylic acid and from '0 to 10 moles per mole of said salt of a branched chain carboxylic acid, a C to C hydrocarbyl radical being attached to the carbon atom of the carboxyl group of said salt and said acid through a non-aromatic carbon atom, and (2) from an equal to a 10-fold amount, by weight, based on the alkali metal salt of an amino-amide having the formula RI C RII wherein R singly is taken from the group consisting of hydrogen and a lower alkyl radical, R singly is an aliphatic hydrocarbyl radical, R and R together being taken from the group consisting of an alkylene and an alkyleneether radical, R" being a straight chain hydrocarbon radical, and, the carbon atoms in R, R and R totalling at least 11, where n is an integer from 2 to 3.

12. A fuel additive composition soluble in a liquid hydrocarbon fuel of the gasoline boiling range, said additive composition being inductible with said fuel in sparkignition engines, said additive composition consisting of (1) an alkali metal carboxylate compound consisting of an alkali metal salt of a branched chain carboxylic acid and from 0 to 10 moles per mole of said salt of a branched chain carboxylic acid, a C to C hydrocarbyl radical being attached to the carbon atom of the carboxyl group of said salt and said acid through a non-aromatic carbon atom, 2) from an equal to a 10-fold amount, by weight,

based on the alkali metal salt, of an amino-amide having the formula R R N(CHa) n-N R C-R" 

3. A LIQUID HYDROCARBON FUEL OF THE GASOLINE BOILING RANGE FOR SPARK-IGNITION ENGINES, CONTAINING AN ADDITIVE COMPOSITION CONSISTING ESSENTIALLY OF (1) AN ALKALI METAL CARBOXYLATE COMPOUND CONSISTING OF AN ALKALI METAL SALT OF A BRANCHED CHAIN CARBOXYLIC ACID AND FROM 0 TO 10 MOLES PER MOLE OF SAID SALT OF A BRANCHED CHAIN CARBOXYLIC ACID, A C4 T C24 HYDROCARBYL RADICAL BEING ATTACHED TO THE CARBON ATOM OF THE CARBOXYL GROUP OF SAID SALT AND SAID ACID THROUGH A NON-AROMATIC CARBON ATOM, AND, (2) FROM AN EQUAL TO A 10-FOLD AMOUNT, BY WEIGHT, BASED ON SAID ALKALI METAL SALT, OF AN AMINO-AMIDE HAVING THE FORMULA 